Or do I use a sheet or something underneath? I'm all ready to go, got the mats out, they're laid out and washed (we purchased them years ago as fatigue mats, never used them, I suppose it is good to hang on to some things). I soaked the Moondance Wingspan with a little soap and tepid water, rinsed and squeezed out excess moisture with cloths. I have pins and blocking wires, don't know if I'll need these. TYIA for the help